# Tagged Questions

79 views

### Why we use $\mathbb{R}^{m \times n}$ notation instead of $\mathbb{R}^{n \times m}$?

I just realised, that I use all the time the notation $\mathbb{R}^{n \times m}$, and all books and papers use $\mathbb{R}^{m \times n}$. $\mathbb{R}^{n \times m}$ is more sympathetic for me, because I ...
11 views

### Notation for concatenation of indexed vectors/matrices

Is there any standard notation for concatenation of matrices/vectors where their indices are taken from a set. I have matrices $A_{ij}$ where $(i,j)\in S$. I want to denote a matrix $A$ which is the ...
23 views

### What's the correct notation for a minimum of a row of a matrix?

Let I=1,...,m denote the indexes of the rows of a matrix A Let J=1,...,n denote the indexes of the columns of a matrix A Let xi,j denote the value of the element A[i,j] I need do use a notation to ...
130 views

135 views

### Unsure about a maths symbol

Help, help, help! I've come across this maths symbol, $[n(i,j)]^{0.5}$ where $n$ is a square matrix. Does this mean that it is the $(i,j)$ element of $n^{0.5}$? or $n(i,j)^{0.5}$? source: ...
237 views

### What does the following symbol mean? (direct sum? o-plus? — subject: matrix theory)

In this paper equation 11, the author uses a symbol that is a cross in a circle. I believe I have seen that referred to as a direct sum, but I am not completely sure what that is. $$\bigoplus$$ ...
164 views

### What is this notation relating to the Jacobian matrix operation?

In the below image, in the very bottom-most equation is the partial differential at the end of the equation being multiplied to every element in the inverse Jacobian matrix (and then beta_n added)? Or ...
125 views

### What does this notation mean? Set of real numbers transposed??

In the below: from top of Page 13: http://www.ntuzov.com/Nik_Site/Niks_files/Research/papers/stat_arb/Ahmed_2009.pdf how do you interpret what x is an element of? It looks like the set of real ...
101 views

### Representing $m\times n$ matrix using ordered $n$-tuples and an $m$-tuple

Can a matrix, generally \begin{bmatrix} a_{1,1} &\cdots &a_{1,n} \\ \vdots &\ddots & \vdots \\ a_{m,1} &\cdots &a_{m,n} \end{bmatrix} be represented using ordered ...
108 views

### Ambiguous notation for squared matrix

What does $A^{2}$ mean for square $A$? Is it $AA$ or $AA^{T}$? Sometimes, the result may differ. Or there is no uniform approach?
420 views

### Is there a symbol for matrix multiplication operator?

Title says it all. Is there any specific operator symbol for matrix multiplication? Not just write down side by side but symbols like cross ($\times$).
516 views

### What is the notation for the set of all $m\times n$ matrices?

Given that $\mathbb{R}^n$ is the notation used for n-dimensional vectors, is there an accepted equivalent notation for matrices?
213 views

### $^t$, $^\dagger$, $^*$, $^H$, $^⊤$, and $^T$ : Which is which, and what do each mean?

I think this question's answer(s) will be of profound use to the future generation of human beings who happen to stumble upon the website math.stackexchange.com. What are the differences between ...
72 views

### Simplified matrix notation

There is a mathematical notation to define an array that you can write using standard keyboard characters on one line? for example:   1 3 8 7 10 17 22 6   5 10 23 8 11 98 7 12
75 views

### Is there a name for this given type of matrix?

Given a finite set of symbols, say $\Omega=\{1,\ldots,n\}$, is there a name for an $n\times m$ matrix $A$ such that every column of $A$ contains each elements of $\Omega$? (The motivation for this ...
### $(\mathbf{u}^T\mathbf{v})\mathbf{v} = \mathbf{u}^T(\mathbf{v}\mathbf{v})$ doesn't hold for $\mathbf{u}, \mathbf{v}\in\mathbb{R}^n$ - why?
Suppose I have vectors $\mathbf{u}$ and $\mathbf{v}$ in $\mathbb{R}^n$. It is well defined to write $5\mathbf{v}$ or $c\mathbf{v}$ for scalar $c$. Since the inner product of $\mathbf{u}$ and ...